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Advertiser and Scanner

Posted by userc_19497 Aug 19, 2015

Hello. Here is an example app that is capable of swapping between advertising and scanning.

 

Advertisement

BLE advertisement packets consists of 31 bytes. Each field (i.e. appearance, name, service UUID or similar) has a header of 2 bytes (length and type), meaning that the maximum user payload is 29 bytes. That means the more fields that are packed into one advertisement packet, there are less bytes freed for user payload.

 

Here's an example of advertisement data(AD) from Bluetooth SIG documentation. (pdf attached)

You can view all the different data types and formats in the documentation attached.

 

Advertisement Field

In our SDK, each field is represented by BLE_ADV_FIELD data structure. Here's the definition:

typedef PACKED struct
{
    UINT8 len; //length of field
    UINT8 val; //value of field
    UINT8 data[ADV_LEN_MAX-2]; // This is the data and the biggest one is 31-2 = 29
} BLE_ADV_FIELD;


Notice the length, value, and the actual data in the struct corresponds to how AD is formatted in the example above.

 

You can change the advertisement packet by defining the fields in an array and initializing them.

    BLE_ADV_FIELD adv[2];

     // Format advertisement data.  Data consists of 2 fields.  Standard Advertisement flags
     // and Broadcom Vendor specific data.  The vendor specific data consists of
     // 16 byte UUID and a message "Hello"

     // flags
     adv[0].len     = 1 + 1; // 1 (data length) + 1 (value)
     adv[0].val     = ADV_FLAGS;
     adv[0].data[0] = LE_GENERAL_DISCOVERABLE | BR_EDR_NOT_SUPPORTED;

     adv[1].len     = 23 + 1; // 23 (data length) + (value)
     adv[1].val     = ADV_MANUFACTURER_DATA; // (AD_TYPE == 0xff)
     adv[1].data[0] = 0x0f;  // Broadcom  (Company Identifier 2 bytes)
     adv[1].data[1] = 0x00;

     // Set UUID
     BT_MEMCPY(&adv[1].data[2], mybeacon_uuid, 16);

     // Set "Hello" message
     BT_MEMCPY(&adv[1].data[18], msg, 5);

 

Here are the field values:

// ADV flag values
enum ble_adv_flag_value
{
    ADV_FLAGS                           = 0x01,
    ADV_SERVICE_UUID16_MORE             = 0x02,
    ADV_SERVICE_UUID16_COMP             = 0x03,
    ADV_SERVICE_UUID32_MORE             = 0x04,
    ADV_SERVICE_UUID32_COMP             = 0x05,
    ADV_SERVICE_UUID128_MORE            = 0x06,
    ADV_SERVICE_UUID128_COMP            = 0x07,
    ADV_LOCAL_NAME_SHORT                = 0x08,
    ADV_LOCAL_NAME_COMP                 = 0x09,
    ADV_TX_POWER_LEVEL                  = 0x0A,
    ADV_CLASS_OF_DEVICE                 = 0x0D,
    ADV_SIMPLE_PAIRING_HASH_C           = 0x0E,
    ADV_SIMPLE_PAIRING_RANDOMIZER_R     = 0x0F,
    ADV_TK_VALUE                        = 0x10,
    ADV_OOB_FLAGS                       = 0x11,
    ADV_SLAVE_CONNECTION_INTERVAL_RANGE = 0x12,
    ADV_SERVICE_SOLICITATION_UUID16     = 0x14,
    ADV_SERVICE_SOLICITATION_UUID128    = 0x15,
    ADV_SERVICE_DATA                    = 0x16,
    ADV_TARGET_PUBLIC_ADR               = 0x17,
    ADV_TARGET_RANDOM_ADR               = 0x18,
    ADV_APPEARANCE                      = 0x19,
    ADV_ADVERTISING_INTERVAL            = 0x1A,
    ADV_SERVICE_SOLICITATION_UUID32     = 0x1F,
    ADV_SERVICE_DATA_UUID32             = 0x20,
    ADV_SERVICE_DATA_UUID128            = 0x21,
    ADV_SECURE_CONNECTION_CONF_VALUE    = 0x22,
    ADV_SECURE_CONNECTION_RANDOM_VALUE  = 0x23,
    ADV_INDOOR_POSITION                 = 0x24,
    ADV_3D_INFORMATION_DATA             = 0x3D,
    ADV_MANUFACTURER_DATA               = 0xFF,
};

 

Then, you'll have to call bleprofile_GenerateADVData function to actually generate the AD.

     bleprofile_GenerateADVData(adv, 2);

where the first parameter is the array to BLE_ADV_FIELD and the second is the number of fields.

 

Starting Advertisement

You can start advertising in few different ways.

If you have the BLE_PROFILE_CFG defined for the app, then you can simply start by calling:

   bleprofile_Discoverable(HIGH_UNDIRECTED_DISCOVERABLE, NULL);

 

Or you can start advertising by setting up the advertisement parameters yourself.

   blecm_startAdv(
        HCIULP_ADV_NONCONNECTABLE_EVENT,                // non-connectable undirected advertisement
        160,                                            // adv interval 100 msec
        HCIULP_ADV_CHANNEL_MAP_MASK,                    // all channels
        HCIULP_PUBLIC_ADDRESS,                          // int advAdrType,
        HCIULP_ADV_FILTER_POLICY_WHITE_LIST_NOT_USED,   // int advFilterPolicy,
        HCIULP_PUBLIC_ADDRESS,                          // int initiatorAdrType,
        NULL);

 

Advertisement packets have different types.

The first argument to this function, blecm_startAdv defines the type of the advertisement.

 

Value Passed
Advertisement Type
0x00ADV_IND
0x02ADV_DISCOVER_IND
0x03ADV_NONCONN_IND

You can refer to the "auto-generated API" for more details on this function.

 

 

Scanning

In order to start scanning, you simply need to call blecen_Scan function.

  blecen_Scan(HIGH_SCAN);

 

Or to turn it off: 

  blecen_Scan(NO_SCAN);

 

Advertisement Handler

You need to register a handler if you want to do anything with the advertisement packet in the app create function.

void advertisement_handler(HCIULP_ADV_PACKET_REPORT_WDATA *evt);
...
void basic_create(void)
{
    ...

    // register to process peripheral advertisements
    blecm_RegleAdvReportCb((BLECM_FUNC_WITH_PARAM) advertisement_handler);
    ...
}


 

 

Swapping between Advertiser and Scanner

I have made an example app that swaps its role between advertising and scanning. The files are attached as adv.h and adv.c

The app first starts scanning, but you can change its role by pushing the button on the board. It has a minimum RSSI value, so you'll need to have advertising device close to the scanner in order for the scanner to pick up the advertisement.

 

I was able to put the code into two Tag 3 boards and test their functions.

Here's the app in action.

Both apps started:

 

One of them starts advertising:

 

Roles switched:

 

AD in detail:

Notice how the advertisement data corresponds to how we set the BLE_ADV_FIELD array above.

 

James

userc_19497

LED with PWM

Posted by userc_19497 Aug 17, 2015

Hello, here is how you can turn on an LED using PWM.


Include Library

#include "pwm.h"
#include "gpiodriver.h"


Define Macros

#define LED_RED    26  /* PWM 0 */
#define LED_BLUE   27  /* PWM 1 */
#define LED_GREEN  28  /* PWM 2 */

#define GPIO_PORT(x)  (x/16)
#define GPIO_PIN(x)   (x%16)

#define ENABLE_LED_RED    PWM0_OUTPUT_ENABLE_P26
#define ENABLE_LED_BLUE   PWM1_OUTPUT_ENABLE_P27
#define ENABLE_LED_GREEN  PWM2_OUTPUT_ENABLE_P28

#define DISABLE_LED_GPIO     GPIO_INPUT_ENABLE | GPIO_PULL_DOWN
#define LED_RED_CHANNEL      (PWM0)
#define LED_BLUE_CHANNEL     (PWM1)
#define LED_GREEN_CHANNEL    (PWM2)

     Note: depending on which chip you are using, the GPIO Pins might change


Enable LED

     // enable
     gpio_configurePin(GPIO_PORT(LED_RED), GPIO_PIN(LED_RED), ENABLE_LED_RED, 0); 
     pwm_start( LED_GREEN_CHANNEL, LHL_CLK, 0x000 , 0);

     // pwm_start( id, clk, toggleCount, initCount);
     // Output Voltage  | Toggle Count (Found these values by trial & error)
     // --------------------------------------------
     // ~ (4/4) V_MAX  |    0x000
     // ~ (3/4) V_MAX  |    0x100
     // ~ (2/4) V_MAX  |    0x210
     // ~ (1/4) V_MAX  |    0x315

 

     Note: depending on the hardware configuration, the V_MAX may change


Disable LED

     // disable
     gpio_configurePin(GPIO_PORT(LED_RED), GPIO_PIN(LED_RED), DISABLE_LED_GPIO, 0);
     pwm_disableChannel( 1 << LED_RED_CHANNEL );

 

 

References

BCM2073XS GPIO Basics

Hardware User Guide (SDK 2.x and TAG3 Board)

How to turn on LED

Different Frequencies for PWM

 

James

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